Moisture permeable composite sheet material and process for preparing same



United States Patent 01 hoe 3,520,765 Patented July 14, 1970 MOISTUREPERMEABLE COMPOSITE SHEET ISVIATERIAL AND PROCESS FOR PREPARING AME AlvaW. Bateman, Hendersonville, Tenn., assignor to 5 US. Cl. 161-84 15Claims ABSTRACT OF THE DISCLOSURE A moisture-permeable sheet material isprovided which is useful as a shoe-upper material, has good surfacesmoothness, and is very resistant to damage when subjected tohigh-tension lasting operations during shoe manufacture; said sheetmaterial is made up of a porous substrate fabric (e.g., a nonwovenfabric), and in superposed adherence therewith, a woven fabric made froma blend of synthetic fibers and cotton fibers and having a very specificcombination of properties, and a mass of microporous moisture-permeableflexible polymeric composition which forms a smooth coating on the uppersurface of the product and penetrates the pores of both fabrics wherebythe coating and fabrics are integrally bonded together.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part ofmy patent application Ser. No. 355,436, filed Mar. 27, 1964 and nowabandoned.

BACKGROUND OF THE INVENTION This invention relates to moisture-permeablecomposite leather-like sheet materials useful as shoe-upper materialsand to a process for preparing such sheet materials.

It is well-known in the art that leather-like sheet materials useful asshoe-upper materials can be prepared by impregnating and coating fibrousweb substrates with certain polymeric materials.

One of the problems which shoe manufacturers have encountered during thelasting operations when making shoes from previously-known man-madeshoe-upper materials is the development of surface roughness in thoseareas which require stretching of the material over a last (e.g., in thetoe and quarter areas of the shoe). Even when a carefully preparednonwoven web is used as the substrate, this roughening problem isusually encountered. The roughening pattern seems to be associated witha pattern which is present in the structure of most fibrous substratesprior to application of the polymeric coating.

There has been a longstanding need for a man-made shoe-upper materialhaving good surface smoothness not only in the as-produced relaxed statebut also when under the tension commonly used in the stretching andlasting operations. A material which does not develop noticeableroughness during lasting is sometimes referred to in the art as anonroughening material. There has been a particular need for anonroughening shoe-upper material which is highly resistant to ruptureor other damage to the structure during relatively high tension lastingoperations, as well as being adapted in other important respects for themanufacture of good quality shoes (e.g., having satisfactoryflexibility, moisture permeability, durability and resistance to unduestretching).

Moisture-permeable microporous man-made leatherlike sheet materials aresometimes referred to in the art as poromeric materials.

SUMMARY OF THE INVENTION In a broad sense, the novel product of thisinvention (sometimes referred to herein simply as the sheet material) isa moisture-permeable composite sheet material having:

good surface smoothness when relaxed and when under tension,

utility as a breathable shoe-upper material, and

good resistance to damage when subjected to relatively high tensionlasting operations during shoe manufacture,

said sheet material containing as essential components (A) a poroussubstrate fabric,

(B) a porous woven fabric of a blend of synthetic fibers and cottonfibers in superposed adherence with fabric (A), and having (1) a tensilestrength of at least about 55 pounds per inch in both the warp and filldirections, (2) a break elongation of about 20-30% in both the warp andfill directions, (3) a modulus at 5% elongation of about 20004000 p.s.i.in the warp direction and about 1800-3800 p.s.i. in the fill direction,(4) a thickness of about 5-6 mils, and (5) a smoothness factor of lessthan about 20 mils, and

(C) a mass of microporous moisture-permeable flexible polymericcomposition which forms a smooth coating in superposed adherence withfabric (B), penetrates the pores of fabric (B), penetrates the pores ofat least the uppermost portion of fabric (A), and integrally bonds thecoating and the fabrics together.

DESCRIPTION OF PREFERJRED EMBODIMENTS It is often advisable to use anonwoven fabric as fabric (A); however, any suitable woven fabric canalso be used, for example one which has been subjected to a nappingoperation which produces a suede-like nap on one or both surfaces. Anespecially preferred nonwoven fabric is one which has the structureresulting from hav ing been impregnated throughout its thickness with amoisture-permeable flexible polymeric composition. Such a nonwovenfabric can be prepared for example by the procedure described in Example1 of US. Pat. 3,067,483 issued Dec. 11, 1962 to J. L. Hollowell.

Fabric (B) must be a woven fabric, and it must be made from a blend ofsynthetic fibers and cotton fibers. The synthetic fibers are preferablypolyester fibers (e.g., polyethylene terephthalate); and the weightratio of polyester fibers to cotton fibers in the fabric is preferablyabout 50/50 to /25, still more preferably about 65/35. Other syntheticfibers (e.g., acrylic fibers, olefin fibers or nylon fibers) which arecapable of being combined with cotton fibers and made into a fabrichaving the properties specified above can also be used. One skilled inthe art, in the light of the present disclosure, will have littledifficulty in selecting the proportion and type of synthetic fiber thatgives the best combination of smoothness,

interlayer adhesion and resistance to damage of the sheet materialduring stretching and lasting operations.

Fabric (B) has a smoothness factor of up to about 20 mils, and in someof the best embodiments of the invention the fabric has a smoothnessfactor of about 12-18 mils. The smoothness factor refers to thethickness in mils of the coating of polymeric composition aftercoagulation and drying which hides the surface pattern of fabric (B) sothat the pattern of the fabric is rendered substantially invisible tothe unaided eye.

Best results are usually obtained when fabric (B) has a substantiallysquare weave; also when it is a fabric which has been bleached, desized,and singed on both sides.. Especially beneficial results are obtainablewhen fabric (B) is a fabric which has been stretched in width while wet(e.g., saturated with water) about 2-10% of its greige width and thendried while maintained in the stretched condition. This stretchingoperation is preferably done before the fabric is combined with the massof microporous composition referred to above as component (C). Thestretched and dried fabric does not have to be kept in a dry conditionbefore it is combined with component (C); in fact, a wetting liquid(e.g., water) can be applied to it prior to or during the formation ofthe sheet material in an amount equal to about l-50% based on thecombined weight of fabric and wetting liquid. The thickness of fabric(B) can be slightly outside the range of 5-6 mils, and the tensilestrength can be slightly less than 55 pounds per inch in at least onedirection, without departing from the spirit of this invention and whileachieving the beneficial results of a nonroughening product combinedwith resistance to damage during high tension lasting operations. It isusually advisable however to use a fabric having a tensile strength ofabout 55-68 pounds per inch in both the warp and fill directions.

The properties specified above as essential for the fabric (B) componentare the properties of the fabric before being combined with the othercomponents of the sheet material; it will be understood that at leastone of these properties might undergo enough change during the variousoperations employed in preparing the finished product (e.g., bathing,drying, shrinking, stretching, embossing etc.) so that the property ofthe fabric within the final product is slightly outside the rangespecified.

With reference to component (C) of the sheet material, the polymericcoating on fabric (B), which forms the upper surface of the product,generally has a roughness value of about -1 and a thickness of not morethan about 30 mils, preferably about 12-20 mils. Roughness values ofporomeric materials are determined by Machine Model 1004-50B made byColumbia Vise and Manufacturing Company, Cleveland, Ohio. Using thismachine, the roughness value of a poromeric material is determined byclamping a twelve inch square sample tightly between ring clamps,coating side up, and distending the material upwards by a piano-convexdeformation head to a maximum of one inch above the original plane. Thehead is moved by hydraulic pressure over a period of about 15 seconds.If there is no apparent roughness at the high point the roughness valueis zero; if discernible but insignificant roughness is present theroughness value is one; if more than insignificant roughness is apparentto the naked eye, the roughness value is greater than one and thematerial does not have a sufficiently smooth appearance for mostshoe-upper applications.

The polymeric material of component (C) preferably has a secant tensilemodulus at elongation of over 600 p.s.i., still more preferably aboutSOD-3,000 p.s.i. The secant tensile modulus is the ratio of the stressto the strain at 5% elongation of the polymer sample determined from thetensile stress-strain curve, and is expressed as force per unit area,e.g., pounds per square inch (often expressed as psi). The secanttensile modulus measurement is carried out according to ASTM D-882-64-T, modified as described below.

The secant tensile modulus of the polymer is determined by forming a 5to 20 mil thick continuous voidfree polymer film from a polymericsolution, for example, the solution to be used to form the microporouspolymeric layer of the sheet material of this invention. The film isformed by casting the polymeric solution on a glass plate and thesolution is then dried, e.g., at 105 C. for minutes.

The stress-strain curve which is necessary to calculate the secanttensile modulus of the polymer is preferably obtained on an InstronTensile Tester, using a /2 inch wide specimen cut from the void-freepolymeric film, with about one inch between grips. The followingsettings are preferably used on the Instron Tester to obtain astressstrain curve: chart speed of 10 inches per minute, crosshead speedof 1 inch per minute, and a full scale load of 2 to 5 pounds.

The secant tensile modulus is obtained from the chart of the force vs.strain curve by drawing a line at 5% specimen elongation (strain)parallel to the force axis of the chart. The point at which this lineintersects the force/ strain curve defines the force in pounds necessaryto elongate the specimen 5%. This force value is divided by the initialcross-sectional area of the specimen to give the corresponding stressvalue in pounds per square inch. This stress value is divided by thestrain (0.05) to give the secant tensile modulus.

A preferred polymeric material for component (C) of the sheet materialis one having a polyurethane elastomer content of at least 51% by weightand a vinyl chloride polymer (e.g., polyvinyl chloride) content of up to49% by weight. Pigments and others additives can be added if desired.

The present invention also provides a process for preparing amoisture-permeable composite sheet material which comprises:

(a) providing a porous substrate fabric,

(b) providing a porous woven fabric of a blend of synthethic fibers andcotton fibers, said woven fabric having been stretched while wet atleast 2% in width and then dried while in the stretched condition, saidwoven fabric also having the tensile strength, break elongation,modulus, thickness, and smoothness factor specified above in the broaddescription of the novel sheet material,

(c) providing a liquid polymeric composition which is comprised of apolymer dispersed in a liquid comprising an organic solvent, and whichis capable of being solidified in situ to form a microporous structurewhen bathed and dried according to steps (e) and (f) below,

((1) forming a composite assembly from the components provided in steps(a), (b) and (c) so that said woven fabric is in superposed relationwith said substrate fabric, and so that there is a continuous body ofsaid liquid polymeric composition which not only forms a coating on thetop surface of said woven fabric but also penetrates the pores of saidwoven fabric and the pores of at least the uppermost portion of saidsubstrate fabric, said coating being of sufficient thickness so thatafter step (f) its thickness is less than 30 mils but great enough torender the surface pattern of said woven fabric substantially invisibleto the naked eye,

(e) bathing the liquid polymeric composition of said composite assemblywith a liquid coagulant adapted to extract the organic solvent from saidcomposition until substantially all of said solvent is extracted, and

(f) drying the composite assembly;

steps (e) and (f) causing said composition to solidify in situ andbecome a microporous moisture-permeable structure which forms anadherent smooth coating on the top surface of the resultingmoisture-permeable composite article and which bonds said fabricstogether.

Just before the bathing operation specified in step (e),

the assembly can be exposed to a humid air zone having a suitablerelative humidity (e.g., 40%) and temperature (e.g., 26 C.) until thecoating on the woven fabric has absorbed enough water to cause at leastthe uppermost portion of the layer to coagulate. At least the lastportion of the bathing operation preferably employs a bathing liquidwhich can easily be removed from the sheet material by evaporation in aheat zone.

In a preferred embodiment of the process described above, step (d) iscarried out by placing said woven fabric in superposed contact with saidsaid substrate fabric to form a composite fabric,

applying a layer of said liquid polymeric composition on the top surfaceof the composite fabric, and

allowing the lower portion of the layer of liquid polymeric compositionto flow downward at a pressure not substantially above atmosphericpressure until it penetrates the pores of the woven fabric and the poresof at least the uppermost portion of the substrate fabric as well as anyvoids between the two fabrics.

One very useful type of liquid polymeric composition to use in step (c)of the process is a substantially colloidal polymeric dispersion whichhas been prepared by adding a non-solvent to a polymer solutionaccording to the method described in claim 1 of US. Pat. 3,100,721issued Aug. 13, 1963 to E. K. Holden, US. Pat. 3,208,875 issued Sept.28, 1965 to E. K. Holden (e.g., in Example 1) also describes usefulliquid polymeric compositions, as well as a useful procedure for causingthe composition to solidify in situ to become a microporous moisturepermeable structure. The disclosures of both of these patents areincorporated herein by reference.

The process of the present invention and the product produced can beillustrated by a preferred embodiment wherein the impregnated nonwovenweb of Example 1 of US. 3,100,721 is placed beneath and in close contactwith a woven interlayer fabric composed of yarns of mixed polyesterfibers and cotton fibers in the ratio of 65: 35. This fabric, which iscommonly used in rnens shirtlng, is desired and stretched, while wet, atleast 2% in width prior to use herein and dried to a moisture content ofless than 3% by weight while in the stretched condition. The fabric isalso bleached and double singed on each side when the highest qualityproducts are desired or when the product is to be dyed.

The polymeric dispersion utilized in Example 1 of US. 3,100,721 is thencoated on the upper surface of the interlayer fabric in an amountsufficient to provide a uniform smooth coating over the surface. Thepolymeric dispersion has a viscosity low enough to permit it topenetrate the interlayer fabric and to enter at least a portion of thesubstrate fabric. The quantity of polymeric dispersion applied to theinterlayer is large enough so that even after such penetration andfilling of the interstices of the interlayer fabric and those of thesubstrate fabric, there still remains a coating on the upper surface ofthe interlayer fabric of sufficient thickness so that after coagulationof the polymer therein there is a surface coating of polymeric materialat least 12 mils thick. If the viscosity of the polymeric dispersion islow enough, it will penetrate the interlayer and substrate merely byforce of gravity and without assistance. Where higher viscosities areutilized, suction may be applied to the under side of the substrate, orto the under side of the interlayer before the interlayer is contactedwith the substrate; or the polymeric dispersion may be forced into theinterstices of the interlayer and substrate fabrics by any otherconvenient means. The manner of causing penetration of the interlayerand the substrate fabric by the polymer dispersion is not critical, butit has been found that the application of suction beneath the substrateor the interlayer serves to provide more uniform penetration with leastdisturbance of interlayer characteristics, and produces poromericmaterials having the best combination of nonroughening properties anddelamination resistance. The coated structure is bathed and dried asdescribed above. Products thus produced have a smooth coating ofmicroporous polymeric material over the surface of the interlayer, andthis coating is contiguous with a matrix of the polymeric dispersionextending within and connecting the interstices of the interlayer fabricand the substrate, thereby providing a sturdy bond between the polymericcoating and the substrate.

The resulting sheet material is usually subjected to finishingoperations known to be useful on man-made leatherlike products, forexample dyeing to the desired color, primer coating, coating with aclear topcoat composition, and finally embossing to provide the surfacewith the desired sheen and/or grain pattern.

Leather-like shoe-upper materials are obtainable in accordance with thepresent invention which have a surprisingly beneficial combination ofproperties including (1) a high level or surface smoothness both whenrelaxed and when subjected to high tension lasting operations [e.g., ascommonly employed in the manufacture of mens dress shoes], (2) excellentresistance to rupture or other damage to the sheet structure during hightension lasting operation, and (3) suitable flexibility,moisturepermeability, wear resistance, delamination resistance, andresistance to undue stretching during shoe manufacturing opeations aswell as during use of the shoe. It is quite unexpected to obtain all ofthese desirable properties in a single man-made shoe-upper material.

The sheet material of this invention usually has a bond strength(delamination resistance) of about 3 pounds per inch or more betweencoating and interlayer fabric and between interlayer fabric andsubstrate fabric. Also, the product usually has a permeability value ofabout 3000 or more, as determined by the test described by Kanagy andVickers in the Journal of American Leather Chemists Association, 45,211-242 (Apr. 19, 1950). The strength of the adhesive bond between theinterlayer and substrate is determined by taking a 1" X 6" sample andcutting it across the width sufficiently deep so that the interlayer canbe separated from the substrate for a length of about 2 inches. Thesample is then placed in an Instron tensile strength tester and thetensile strength of the adhesive bond measured using a crosshead speedof 10 inches per minute, a chart speed of 2 inches per minute and a jawgap of 2 inches. Strength of the adhesive bond between the polymericcoating layer and the interlayer is determined similarly. Both can bereferred to as delamination bond strengths.

The examples which follow are given for the purpose of illustrating theinvention. All quantities shown are on a weight basis unless otherwiseindicated.

EXAMPLE 1 A sheet material having outstanding utility as a breathableshoe-upper material is prepared as follows. A substrate consisting of aporous impregnated needlepunched nonwoven web like that utilized inExample 1 of US. 3,100,721 is brought into contact with an interlayermaterial consisting of a woven fabric composed of yarns made up of ablend of 65% polyethylene terephthalate fibers and 35% cotton fibers,the fabric having a greige count of 96 x 96 (warp x fill). Theinterlayer fabric is one that has been desized by conventional methodsand then stretched while wet from an initial width of 47 inches to afinal width of 49 inches, and dried while in the stretched condition,using a conventional tenter frame. By this procedure the fabric, whichinitially had a tensile strength of 62 x 65 pounds per inch, a modulusof 3400 x 1200 pounds per square inch at 5% elongation and a breakelongation of 26% x 35%, was converted to a fabric having a tensilestrength of 59 x 62 pounds per inch, a modulus of 3000 x 2600 pounds persquare inch at elongation, a break elongation of x 25%, a smoothnessfactor of 14 mils, a thickness of 5.5 mils and weight of 2.3 ounces persquare yard. Thickness is determined by ASTM D-1813-60T.

The nonwoven fibrous substrate is one that had been previouslyimpregnated with a polyurethane dispersion composition corresponding tothat utilized below and then dried so that the impregnated substratecontained 50% dispersion solids based on the weight of fibers.

The interlayer fabric is placed on top of the impregnated substrate, andthe polymer dispersion in a dimethyl formamide/water mixture, preparedin accordance with Example 1 of U.S. 3,100,721, is coated on the uppersurface of the interlayer sheet in the amount of 3.75 pounds dispersionper square yard of surface coated. The coated structure is subjected tosuction (5 inches of mercury vacuum) from the under side of thesubstrate layer for a few seconds, which is sufficient to draw thepolymer dispersion through the interlayer material and partially intothe substrate layer, forming a continuous matrix connecting the twolayers. The amount of suction and the length of time it is applied isregulated so that sufficient polymer dispersion remains on the upperside of the interlayer fabric to provide a coating about 18 mils thickafter coagulation and drying. About one-half minute after suction isreleased, during which time the polymeric dispersion fiows out and formsa smooth coating on the upper surface of the interlayer material whileundergoing a partial coagulation or precipitation reaction as a resultof its exposure to the moisture in the atmosphere, the laminatedstructure is immersed in a tank which contains water at room temperatureand is bathed in this water for about 3 minutes. Finally, the product isimmersed in another water bath at C. until the polymer is completelycoagulated. Residual solvent is leached from the product by furtherbathing in water, and then the coated substrate is subjected to hot airat 120 C. until dry.

The resulting sheet material, which has an unusually beneficialcombination of shoe-making characteristics, has a permeability value of9000, a very smooth surface, and a high level of rupture resistance. Thepreparation of the product for use in the manufacture of shoes iscompleted by:

(1) dyeing the sheet material brown by (a) dipping it in water at 94 C.for 20 seconds, (b) passing it between a pair of nip rolls to reduce thewater content to (c) dipping it for one minute in a brown aqueous dyebath having a pH of 10.2 and a temperature of 94 C., and containing 3%of a brown dye (CI 20110), (d) passing it between a pair ofrubber-covered nip rolls under a pressure of pounds per inch (width ofthe sheet), (e) dipping it for seconds in an aqueous dichromate solutionhaving a temperature of 94 C. and containing 4 grams per liter of sodiumdichromate and 2 grams per liter of acetic acid, (f) passing it betweena pair of nip rolls under a pressure of pounds per inch, (g) dipping itin water at 94 C. for 4 minutes, (h) passing it between a pair of niprolls at 125 pounds per inch, and (i) drying the dyed sheet in an ovenat 121 C. for 5 minutes;

(2) applying to the top surface of the sheet by means of a sprayer 0.18ounce per square yard (dry'basis) of a brown acrylic emulsion primercoat and drying the primer coat in a heat zone at C.

(3) applying to the primer-coated surface by means of a sprayer 0.15ounce per square yard (dry basis) of a brown acrylic emulsion base coatand drying the base coat in a heat zone at 140 C.;

(4) applying to the base-coated surface of the sheet 0.05 ounce persquare yard (dry basis) of a clear top coat and drying the sheet in aheat zone at 140 C., the top coat composition being at 3.4% solution ofa 60:40 blend of plasticizer and cellulose acetate butyrate in a blendedvolatile organic solvent; and

(5) hot-press embossing the sheet by passing it over a roller heated toC. to preheat it and then passing it through an embossing apparatusgenerally as described as the preferred embodiment of U.S. Pat.3,157,723 issued Nov. 17, 1964 to J. Hochberg; the surface of the 12inch diameter roller which contacts the coated surface of the sheet isengraved to provide the surface of the sheet with a fine leather-likegrain pattern; the roller has a temperature of 160 C.; each square inchof the sheet is in the nip for a period of 18 seconds (the sheet movesat 3 feet per minute through a nip having a length of 1.5 feet) under apressure of 13 p.s.i.g. The sheet is then cooled to room temperature,and the bottom surface is buffed on a machine commonly used for raisinga nap on fabrics, using an emery cloth covered roll, until a uniform napis produced. The coating compositions used in steps 2 and 3 are asfollows:

The product of Example 1 has the following combination of desirableshoe-making characteristics:

extremely smooth appearing surface, both when relaxed and when subjectedto the high tension lasting operations commonly employed in themanufacture of mens dress shoes; the product has a roughness value of 0;

excellent resistance to rupture during high tension lasting operations;

relatively economical and easy to manufacture in substantially uniformquality by a continuous mass pro: duction method;

good resistance to delamination, the bond strength being 4.5 pounds perinch between the coating and the woven fabric as well as between the twofabric layers;

good wear resistance, breathability and comfort properties when madeinto mens dress shoes and subjected to normal use;

coating thickness of 18 mils and product thickness of 62 mils; and

good resistance to undue stretching during conventional shoemanufacturing operations and during normal use of the resulting shoes.

The product of Example 1 is also useful as a breathable upholsterymaterial, particularly in applications requiring a very smooth orfine-grain finish in combination with high resistance to rupture duringfabrication and use of the upholstered product.

Under conditions representative of a typical production run in a shoefactory, 5000 pairs of mens dress shoes (10,000 shoes) are made from theproduct of Example 1 by a conventional shoe-making procedure wherein theshoe-uppers are subjected to high tension stretching and lastingoperations which result in an elongation of the upper material in thetoe area of about 9-12% or more. The product of Example 1 is found tohave excellent shoe-making characteristics throughout the productionrun, and all of the shoes are of satisfactory quality. None of the shoesshow any signs of rupture or other damage to any portion of the uppermaterial, either before or after the shoes are subjected to normal use.

9 Example 1A For purposes of comparison, a shoe-upper material outsidethe scope of this invention is prepardd in the manner described inExample 1 except the woven fabric used in the present example as theinterlayer fabric is a cotton lawn fabric which (a) has been made fromyarns composed of 100% cotton fibers, the greige fabric having 5.00 x 40weight yards per pound at 40 inch width), (b) has been desized and thenslack mercerized in 23% sodium hydroxide solution to reduce the fabricsurface area (one side) 12% below the surface area of the greige fabric,(c) has been bleached and then double singed on both sides, and (d) hasa thread count of 123 x 118, a weight of 2.6 ounces per square yard, atensile strength of 50 x 50 pounds per inch, a break elongation of x15%, a modulus at 5% elongation of 720 x 1200 psi, a thickness of 5 milsand a smoothness factor of less than mils.

The product of Example 1A is useful for the manufacture of shoes andupholstery, but not nearly as useful as the product of Example 1. Animportant drawback of the Example 1A product is its limited ruptureresistance, which is illustrated as follows.

In the manner described in the latter portion of Example 1, 5,000 pairsof mens dress shoes are made from the product of Example 1A. Many of theresulting shoes are not of satisfactory quality. In fact, 800 of theshoes (8%) had to be destroyed as unsatisfactory for sale because ofdamage to the upper material (e.g., rupture of the fabric portion of thestructure) which occurred mostly in the toe area during the high tensionlasting operations. The shoes having the damaged uppers had an uglygroove in the damaged area (e.g., about A" wide and about /2-1" long)which rendered them unsatisfactory in appearance. Furthermore, 300 ofthe shoes (3%) had satisfactory appearance before being worn butdeveloped an ugly crack in the toe area during normal use. Thus, a totalof 1100 shoes were rendered unsatisfactory due to damage to the uppermaterial during conventional shoe fabrication operations.

I claim:

1. A moisture-permeable composite sheet material havmg:

good surface smoothness when relaxed and when under tension,

utility as a breathable shoe-upper material, and

good resistance to damage when subjected to relatively high tensionlasting operations during shoe manufacture,

said sheet material containing as essential components:

(A) a porous substrate fabric,

(B) a porous woven fabric of a blend of synthetic fibers and cottonfibers in superposed adherence with fabric (A), and having (1) a ten-,sile strength of at least about 55 pounds per inch in both the warp andfill directions, (2) 3 a break elongation of about 20-30% in both thewarp and fill directions, (3) a modulus at 5% elongation of about2000-4000 p.s.i. in the warp direction and about 1800-3800 p.s.i. in thefill direction, (4) a thickness of about 5-6 mils, and (5) a smoothnessfactor of less than about 20 mils, and

(C) a mass of microporous moisture-permeable flexible polymericcomposition which forms a smooth coating in superposed adherence withfabric (B), penetrates the pores of fabric (B), penetrates the pores ofat least the uppermost portion of fabric (A), and integrally bonds thecoating and the fabric together.

2. A sheet material according to claim 1 wherein fabric (A) is anonwoven fabric.

3. A sheet material according to claim 2 wherein said nonwoven fabrichas the structure resulting from having been impregnated throughout itsthickness with a moisture-permeable flexible polymeric composition.

4. A sheet material according to claim 1 wherein fabric (B) has asubstantially square weave.

5. A sheet material according to claim 1 wherein fabric (B) is a fabricwhich has been bleached, desized, and singed on both sides.

6. A sheet material according to claim 5 wherein fabric (B) is a fabricwhich has been stretched in width while wet about 2-10% of its greigewidth before being combined with said mass of microporous composition.

7. A sheet material according to claim 1 wherein fabric (B) consistsessentially of a blend of polyester fibers and cotton fibers.

8. A sheet material according to claim 7 wherein the weight ratio ofpolyester fibers to cotton fibers in fabric (B) is about 50/50 to 75/25.

9. A sheet material according to claim 8 wherein said weight ratio isabout 65/35.

10. A sheet material according to claim 1 wherein fabric (B) has atensile strength of about 55-68 pounds per inch in both the warp andfill directions.

11. A sheet material according to claim 1 wherein the coating inspperposed adherence with fabric (B) has a thickness of less than about30 mils and a roughness value of about 0-1.

12. A sheet material according to claim 11 wherein said coating has athickness of about 12-20 mils.

13. A process for preparing a moisture-permeable composite sheetmaterial which comprises:

(a) providing a porous substrate fabric,

(b) providing a porous woven fabric of a blend of synthetic fibers andcotton fibers, said woven fabric having been stretched while wet atleast 2% in width and then dried while in the stretched condition, saidwoven fabric also having the tensile strength, break elongation,modulus, thickness, and smoothness factor specified in claim 1,

(0) providing a liquid polymeric composition which is comprised of apolymer dispersed in a liquid comprising an organic solvent, and whichis capable of being solidified in situ to form a microporous structurewhen bathed and dried according to steps (e) and (f) below,

(d) forming a composite assembly from the components provided in steps(a), (b) and (c) so that said woven fabric is in superposed relationwith said substrate fabric, and so that there is a continuous body ofsaid liquid polymeric composition which not only forms a coating on thetop surface of said Woven fabric but also penetrates the pores of saidwoven fabric and the pores of at least the uppermost portion of saidsubstrate fabric, said coating being of sufficient thickness so thatafter step (f) its thickness is less than 30 mils but great enough torender the surface pattern of said woven fabric substantially invisibleto the naked eye,

(e) bathing the liquid polymeric composition of said composite assemblywith a liquid coagulant adapted to extract the organic solvent from saidcomposition until substantially all of said solvent is extracted, and

(f) drying the composite assembly; steps (e) and (f) causing saidcomposition to solidify in situ and become a microporousmoisture-permeable structure which forms an adherent smooth coating onthe top surface of the resulting moisturepermeable composite article andwhich bonds said fabrics together.

14. A process according to claim 13 wherein step (d) is carried out by:

placing said woven fabric in superposed contact with said substratefabric to form a composite fabric,

applying a layer of said liquid polymeric composition on the top surfaceof the composite fabric, and

allowing the lower portion of the layer of liquid 11 12 polymericcomposition to flow downward at a pres- References Cited surtcl notsugtstatrtialtlfi above atfmolspheric prizssburr: UNITED STATES PATENTSun1 1 pen ra s e pores o e woven 1 and the pores of at least theuppermost portion of 3418'198 12/1968 Emstman 161-159 the substratefabric as well as any voids between 5 ROBERT F. BURNETT, PrimaryExaminer the two fabrics. 15. A process according to claim 14 whereinsaid Assistant Examiner woven fabric consists essentially of a blend ofpolyester fibers and cotton fibers in a weight ratio of about 50/50 to75/25. 10 117-161; 156-77; 161-81, 90, 151, 159

